Many types of gas-plasma display devices are now in wide use. All of these devices include electrodes, electrode leads and various forms of dielectric layers. The dielectric layers perform several functions including providing an undercoating for electrodes, insulating electrodes from each other, covering conductor runs, and the like. These dielectric layers are formed by depositing a dielectric composition on a soda-lime glass plate and then firing to form the desired layer.
These dielectric compositions generally consist of a glass frit, one or more refractory fillers, an inorganic pigment and an organic vehicle. Such compositions are usually referred to as pastes or inks. In using such materials, various factors including optical, physical and electrical characteristics must be taken into account; and, in selecting the glasses for these dielectrics, the primary factors to consider are the thermal coefficient of expansion and softening and working temperatures.
Up to the present time, glasses suitable for use in various types of display panels employing sodalime float glass as the preferred substrate material have all included lead. Only lead glasses were found capable of achieving the required characteristics, including a working temperature below 590.degree. C., which is necessary to prevent distortion of the glass substrate. As is well known, lead is an undesirable element to have present in the manufacturing process. These lead glasses are degraded by thermal processing during fabrication operations and by high electric fields such as those encountered during device operation. In addition, the use of lead-bearing glasses presents a potential environmental and personnel health problem, and complex and expensive protective measures are required to alleviate these problems.
The present invention provides a new dielectric composition which includes a lead-free glass frit and is usable in display panels and the like devices. This composition is formulated to provide a multilayer dielectric coating to isolate layers of conductor runs and a mask dielectric coating to provide a low-cost glass, black insulation layer between conductor runs and the gas plasma.